pH meters of varying types and quality are helpful for the knowledge of pH of liquids. They can be simple and low-cost pen-like devices to complex lab instruments with computer interfaces and several inputs. Applications of pH meters include measurement of quality of water in water supply systems, soil measurements in agriculture, testing quality of disinfectants and sterilants in healthcare systems, and more.
Measuring pH using basic potentiometric pH meters involves measurement of voltage between two electrodes, converting this value into the corresponding pH value and sending this value to a display often calibrated in pH. The design involves a few low-cost and standard electronic components such as an electronic amplifier and display along with a specialized probe. The glass probe is dipped into the solution whose pH or hydrogen ion concentration is to be determined. For very precise measurements, frequent calibration of pH meter with solutions of known pH is necessary before each measurement. Specialized probes are available for measurement in harsh environments.
The following section discusses some industrial-grade pH meter reference designs along with complete documentation:-
- Isolated Low Power pH Monitor: This reference design provides a completely isolated low power pH sensor suitable for a variety of industrial applications such as chemical, food processing, water, and wastewater analysis. The design provides automatic temperature compensation for high accuracy. Supporting a wide variety of pH sensors with high internal impedances, the circuit gives 0.5% accurate readings for pH values from 0 to 14 with greater than 14-bits of noise-free code resolution. Digital signal and power isolation provides immunity to noise and transient voltages often encountered in harsh industrial environments. More on this Reference Design
- Wireless pH Sensor Transmitter: This reference design shows how to build an industrial-grade wireless pH transmitter for process control. The design has overall tested accuracy of +/- 0.01pH for input range 0 to 14 pH. The firmware used for testing and characterization is Bluetooth Smart, which has the highest presence ratio in portable equipment, making testing and demonstration easier. The design includes PT100 for temperature compensation and supports a temperature range of -40 to +125C. More on this Reference Design